1. Field of the Invention
This invention relates to reserve type primary galvanic batteries. In particular, it relates to reserve batteries which operate by immersion in seawater.
2. Description of the Prior Art
There is a class of batteries employing zinc, aluminum or magnesium anodes and silver chloride, copper chloride or lead chloride cathodes which are activated by and operate submerged in a weak aqueous electrolyte such as seawater. Such batteries are completely inactive until immersion. Batteries of this type have been used in considerable quantity in ocean waters. The equipment with which they are associated is often of the non-recoverable sort. Also, the use perod is often limited to a few hours.
It has been a prime objective of designers of such batteries to seek ways to simplify the constructional details of the batteries so as to reduce costs both with respect to the materials used therein and with respect to the labor required to assemble the batteries.
In a number of known devices, bipolar plate subassemblies are used. By this term is meant a subassembly comprising the anode of a first cell, the cathode of a second cell and a barrier impervious to electrolyte located between the two electrodes. A number of such bipolar plates are piled together with terminal anode and cathode at opposite ends and the barriers properly sealed to a container resulting in a multicell battery. In many bipolar subassemblies the barrier is a metal sheet contacting the anode on one side and the cathode on the other. This provides a very low resistance electrical path from anode to cathode of adjacent cells. It provides a strong support for both anode and cathode. However, the choice of metal is somewhat limited since it must be electrochemically compatible with both anode and cathode. It must be free from attack by the electrolyte, it must not passivate by contact with the electrolyte and it must avoid local action effects. Further, a metal barrier will add weight to the battery assembly when compared to a battery having non-metallic barriers. Bipolar plates having electrodes attached to either side of a molded plastic barrier are known. With this design, a lip having a thickness equal to that of the length of a cell may be molded about periphery perifery of the barrier. A battery is built from such bipolar subassemblies simply by cementing the lip of one barrier to that of the next. However, costly dies are required for the molding of such barriers. Also, there is a limit to the thinness to which a molded part can be made. The limit is about 0.5 mm or greater.
Assemblies are known where a series of bipolar subassemblies with barriers extending outwardly therefrom are dipped into a suitable plastic material for a short time. The plastic material bridges the gap from barrier to barrier and, upon setting, forms a shell or battery casing.